   (> (get-loan-amount m)
      417000))
 
-(def foo (make-mortgage 500000 0.035 0.15))
+(s/defn total-mortgage-price :- s/Num
+  [m :- Mortgage]
+  (* (get-loan-amount m)
+     (Math/pow e
+               (* (:apr m)
+                  (:num-years m)))))
+
+(s/defn base-monthly-payment :- s/Num
+  [m :- Mortgage]
+  (/ (total-mortgage-price m)
+     (* (:num-years m)
+        12)))
+
+; ok so the math should look something like
+; amount = P * e^rt
+; so is that eg 500,000 * e ^ (0.035 * 30) ?
+
+(def foo (make-mortgage 500000 0.0325 0.2 30))
 
 (comment
   (get-loan-amount foo)

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  (s/fn-schema get-loan-amount)
  (s/fn-schema make-mortgage)

  (total-mortgage-price foo)
  (base-monthly-payment foo)

  )
